IMPACTS OF 2,4-DICHLOROPHENOXYACETIC ACID AQUATIC HERBICIDE FORMULATIONS ON REPRODUCTION AND DEVELOPMENT OF THE FATHEAD MINNOW (PIMEPHALES PROMELAS)

The authors studied the effects of 2 formulations of 2,4-dichlorophenoxyacetic acid, dimethylamine salt (2,4-D) herbicide on fathead minnow reproduction, embryonic development, and larval survival. Groups of reproductively mature fathead minnows were exposed for 28 d to 0.00 ppm, 0.05 ppm, 0.50 ppm, and 2.00 ppm 2,4-D (target) in a flow-through system. Weedestroy(R) AM40 significantly (p <= 0.05) depressed male tubercle presence and significantly increased female gonadosomatic index, and there were statistical trends (0.05 <= p <= 0.10) for effects on fecundity and hepatic vitellogenin mRNA expression in females and males. The herbicide DMA(R) 4 IVM also significantly depressed male tubercle presence. Gonads of females exposed to DMA 4 IVM exhibited significantly depressed stage of oocyte maturation, significantly increased severity of oocyte atresia, and a significant presence of an unidentified tissue type. Also, DMA 4 IVM significantly decreased larval survival. It had no impact on hepatic vitellogenin mRNA expression or gonadosomatic index. No significant effects on fertilization, hatchability, or embryonic development were observed in either trial. The formulations tested exhibited different toxicological profiles from pure 2,4-D. These data suggest that the formulations have the potential for endocrine disruption and can exert some degree of chronic toxicity. The present use of 2,4-D formulations in lake management practices and their permitting based on the toxicological profile of 2,4-D pure compound should be reconsidered. (C) 2015 SETAC